Extended scan depth optical coherence tomography for evaluating ocular surface shape

Abstract

Abstract. Spectral domain optical coherence tomography (SD-OCT) with extended scan depth makes it possible for quantitative measurement of the entire ocular surface shape. We proposed a novel method for ocular surface shape measurement using a custom-built anterior segment SD-OCT, which will serve on the contact lens fitting. A crosshair alignment system was applied to reduce the misalignment and tilting of the eye. An algorithm was developed to automatically segment the ocular surface. We also described the correction of the image distortion from the segmented dataset induced by the nontelecentric scanning system and tested the accuracy and repeatability. The results showed high accuracy of SD-OCT in measuring a bicurved test surface with a maximum height error of 17.4 μm. The repeatability of in vivo measurement was also good. The standard deviations of the height measurement within a 14-mm wide range were all less than 35 μm. This work demonstrates the feasibility of using extended depth SD-OCT to perform noninvasive evaluation of the ocular surface shape. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Automatic Segmentation of the Central Epithelium Imaged With Three Optical Coherence Tomography Devices

“…As described, X-Y cross aiming was used with all three devices for fine adjustment of the pupil center. 22 Images were acquired when both aiming windows showed specular reflex on the corneal apex, which indicated that the incident OCT beam was perpendicular to the apex. All the images were acquired by the three OCT devices within half an hour.…”

Ultrahigh Speed OCT

“…The first demonstration of anterior segment OCT imaging was performed in 1994 by Izatt et al [63]. Multiple studies demonstrated time-domain OCT and Fourier-domain OCT for anterior segment imaging at different wavelengths and speeds [11,22,[64][65][66][67][68]. Challenges encountered in SD-OCT could be addressed by reducing parasitic sensitivity roll-off and improving light penetration into tissue [69,70].…”

Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography

“…Briefly, the first step was to automatically seg- [36,37]. In this step, the initial anterior corneal boundary was primarily estimated by thresholding and binary morphology [30]. Then, a shortest path search using dynamic programming was applied to optimize the boundary position.…”

“…As described previously [29][30][31][32][33][34][35], the long scan depth SD-OCT system has a superluminescent diode light source (Superlumdiodes Ltd., Moscow, Russia) with a wavelength centered at 840 nm. The axial resolution was ∼7.5 μm in the cornea tissue.…”

“…In previous studies, a long scan depth SD-OCT system was able to image the entire cornea [29][30][31]. However, the repeatability and reproducibility of entire corneal pachymetric measurements using SD-OCT have not been investigated.…”